Mavenize existing eclipse project

It is very easy, you should just change .project file of your eclipse project..

You should add below xml snippet to under element of .project file.

<buildCommand>
   <name>org.maven.ide.eclipse.maven2Builder</name>
   <arguments>
   </arguments>
  </buildCommand>
   
  
And also you should add below xml snippet under element of .project file.

<nature>org.maven.ide.eclipse.maven2Nature</nature>

edit :

Below snipped should be included .classpath file.

<classpathentry kind="con" path="org.maven.ide.eclipse.MAVEN2_CLASSPATH_CONTAINER">
   <attributes>
    <attribute name="org.eclipse.jst.component.dependency" value="/WEB-INF/lib"/>
   </attributes>
 </classpathentry>